\documentclass{beamer} 
\usepackage{tikz} 
\usetikzlibrary{mindmap} 
\begin{document} 
\begin{frame} 

  \onslide<1->
  { 
    \tikzstyle{hardfaults} = [concept color=black!50,opacity=0] 
    \tikzstyle{softfaults} = [concept color=black!50,opacity=0] 
    \tikzstyle{isolation} = [concept color=black!50] 
    \tikzstyle{accommodation} = [concept color=black!50]
  } 
  \only<2->{\tikzstyle{hardfaults} = [concept color=green!50!black]} 
  \only<3->{\tikzstyle{softfaults} = [concept color=green!50!black]} 
  \only<4->{\tikzstyle{isolation} = [concept color=red!50!black]} 
  \only<5->{\tikzstyle{accommodation} = [concept color=red!50!black]} 

  \begin{figure} 
    \begin{tikzpicture}[scale=0.8,transform shape,mindmap, text=white] 
      \node [concept] {FDI\\requirements} [clockwise from=0] 
      child [hardfaults] { 
        node[concept] (nav) {Hard faults\\detection} 
      } 
      child [softfaults] { 
        node[concept] (nav) {Soft faults\\detection} 
      } 
      child [isolation]{ 
        node[concept] (ctrl) {Isolation} 
      } 
      child [accommodation] { 
        node[concept] {Accommo-\\dation} 
      } 
      ; 
    \end{tikzpicture} 
  \end{figure} 

\end{frame} 
\end{document}
